Drilling rig system with self-elevating drill floor

ABSTRACT

A transportable drilling rig having a self-elevating drill floor includes a base structure comprising multiple base towers that can be transported to a wellsite and positioned around an intended wellbore location. A horizontal base frame is installed between lower regions of the towers to form a stable rig base structure, and a drill floor can then be constructed over the base frame and between the base towers. A suitable rig mast can then be erected on the drill floor. Floor-lifting cables are anchored to upper regions of the base towers and disposable around corresponding sheave assemblies associated with the drill floor. The free ends of the floor-lifting cables can be engaged by the traveling block in the rig mast, whereupon the rig&#39;s drawworks can be actuated to elevate the drill floor and mast as required and then locked to the base towers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/492,786, filed on Jun. 2, 2011, and said earlier application isincorporated herein by reference in its entirety for continuity ofdisclosure.

FIELD OF THE DISCLOSURE

The present disclosure relates in general to rig structures for drillingwells such as oil and gas wells. In particular, the disclosure relatesto rig structures that can be readily transported, rapidly erected, andrapidly disassembled, and further relates to methods for erecting suchrig structures.

BACKGROUND

Wells for the recovery of hydrocarbons or minerals from a subsurfaceformation are commonly drilled by connecting a drill bit onto the lowerend of an assembly of drill pipe sections connected end-to-end (commonlyreferred to as a “drill string”), and then rotating the drill string sothat the drill bit progresses downward into the earth to create thedesired wellbore. The drill string is typically rotated by means of a“rotary table” or a “top drive” associated with a drilling rig erectedat the ground surface over the wellbore.

The primary components of a typical drilling rig include a base supportstructure, a drill floor, and a mast (also called a derrick) supportedon and extending upward from the drill floor. The drill floor istypically elevated well above the ground surface to provide space toaccommodate and allow access to various equipment required for drillingoperations. An arrangement of pulleys (sheaves) called a crown block ismounted to the top of the rig mast. Hoisting apparatus called adrawworks, comprising a cable drum, a cable winch, and ancillaryequipment, is provided in association with the drill floor. Wire-ropecable is fed from the cable drum up to the crown block and threaded overthe various sheaves in the crown block, and then down to a “travelingblock”, which is an assembly of sheaves that is free to move verticallywithin the mast structure as the wire-rope cable (“drill line”) isplayed out or taken up by the cable winch and drum of the drawworks. Thetraveling block has a lifting hook to support equipment used to raiseand lower the drill string, and to add pipe sections during drill stringassembly (or “make-up”) and to remove pipe sections during drill stringdisassembly (“break-out”). For drilling operations using a top driveinstead of a rotary table to rotate the drill string, the top drive issuspended from the traveling block hook.

For optimal efficiency and economy in well-drilling operations, it isdesirable for drilling rigs to be readily transportable, rapidlyerected, and rapidly disassembled for transportation to new wellsites.Accordingly, the transportability of rig components and the speed atwhich components can be assembled with the minimum amount of auxiliaryequipment are paramount concerns. Conventional types of transportablerigs may require auxiliary support equipment to facilitate the erectionand disassembly of large components such as the base, the drill floor,and the pipe racking board, thereby increasing rig set-up, take-down,and operational costs.

Numerous types of transportable rigs may be found in the prior art.Known transportable rigs commonly feature what is called a “bootstrapmast”. A bottom mast section having a large lower opening on one side ismounted to the drill floor, using a mobile crane. The crane then lowersthe top section of the finished mast (housing the crown block) into thebottom mast section, and the top mast section is temporarily pinned tothe bottom mast section. Next, the crane positions an intermediate mastsection through the opening in the bottom mast section so that the upperend of the intermediate mast section can be securely connected to thelower end of the upper mast section. The traveling block is then loweredto engage and support the intermediate section, the upper mast sectionis unpinned from the bottom mast section, the drawworks is actuated tohoist the upper and intermediate mast sections a distance correspondingto the height of the intermediate mast section, and then thepartially-constructed mast assembly (i.e., upper section plus oneintermediate section) is temporarily pinned to the stationary bottommast section. This latter process is then repeated as necessary toinstall additional intermediate mast sections until the mast has reachedits intended final height, whereupon the lowermost intermediate mastsection is secured to the bottom mast section so that the rig is readyto be put into service.

Drilling sites are often located in remote areas requiring trucktransportation of rig components and equipment required for rig assembly(or “rig-up”). Further complicating the rig-up process is the commonneed to relocate the rig to a more promising site after a wellbore hasbeen drilled and it has been determined that the wellbore will not besufficiently productive to warrant completion and operation of the well.Wellsite changes can occur once every several months, and, in response,prior art rig systems have attempted to increase the mobility of rigcomponents and the efficiency of rig erection and disassembly proceduresin order to minimize associated costs. However, the need for auxiliaryequipment typically remains necessary for performing steps such asplacing the drill floor.

Since the variable costs associated with leased support equipment, suchas cranes and the like, are calculated on a per hour or per day basis,expediting rig take-down, transport, and set-up operations is crucialfor minimizing equipment leasing costs. Typically, rig take-down andset-up times are in the order of days, and very large equipment andlabor costs can be incurred for each end of a set-up and take-downoperation. Various prior art drilling rigs are geared towardsfacilitating rapid set-up, take-down and transport, but they stillrequire auxiliary equipment such as external cranes and externalwinches, which most often need to be leased and therefor increaseoverall rig set-up and take-down costs, particularly for remotewellsites.

One approach to reducing rig set-up times and costs is to raise thedrill floor to its intended service elevation after erection of themast. This results in economies due to the fact that the mast can beerected with the drill floor close to ground level rather than in itsfinal position 20 feet or more above ground. The cranes and otherequipment manipulating and positioning the various drill floor and mastcomponents do not require as high a reach, and workers have more readyaccess to the drill floor during rig-up procedures.

An example of a transportable drilling rig having a drill floor that canbe raised after mast erection can be seen in U.S. patent applicationSer. No. 12/492,980 (Wasterval), Pub. No. US 2012/0326734A1. Wastervalteaches the construction of a drill floor over a base structure, whichis provided with hydraulic cylinders for raising the drill floor abovethe base structure. After the drill floor has been raised by anincrement corresponding to the stroke of the hydraulic cylinders, afirst set of box beams are disposed between the drill floor and the basestructure, and the box beams are anchored to the drill floor. The liftcylinders on the base structure can then be retracted to engage liftpoints on the box beams. The lift cylinders are then actuated again,this time to raise both the drill floor and the first box beams anchoredthereto. This allows insertion of a second set of box beams between thebase structure and the first set of box beams, thus elevating the drillfloor a further incremental amount. This procedure is repeated asnecessary to install additional sets of box beams until the drill floorhas reached its intended elevation.

The Wasterval system thus allows the drill floor to be erected orconstructed close to ground level, followed by erection of the rig maston the drill floor, whereupon the drill floor (with erected mast) can beelevated as required. However, this system has an inherent drawback inthat the rig floor raising procedure has to be carried out inincremental and comparatively complex stages, and is correspondinglycomplex and time-consuming. In addition, the Wasterval system entailsthe provision of a robust hydraulic system, which might not otherwise beneeded on site during rig-up, and thus increases rig-up costs. As well,the Wasterval system requires the use of mobile cranes or otherauxiliary hoisting equipment to manipulate and position the box beams,further adding to rig-up costs.

For the foregoing reasons, there is a need for an improved transportabledrilling rig that can be rapidly erected and disassembled with minimalneed for auxiliary equipment. In particular, there is a need for animproved transportable rig in which the drill floor can be elevatedafter erection of the mast, but without requiring hydraulics orauxiliary hoisting equipment.

BRIEF SUMMARY

In general terms, the present disclosure teaches a transportabledrilling rig apparatus having a drill floor that can be elevated aftererection of the rig mast, without requiring a hydraulic system orauxiliary hoisting equipment. In one embodiment, the rig's travelingblock and drawworks are used to elevate the drill floor. In alternativeembodiments, a worm gear drive mechanism can be used to elevate thedrill floor.

The rig apparatus includes a rig base structure comprising a pluralityof base towers that can be positioned in a suitable spaced relationshipon a wellsite. In one embodiment, there are four base towers arranged ina square or rectangular pattern, but other embodiments could use morethan four towers and as few as three, and possibly in different (i.e.,non-rectilinear) patterns. A generally horizontal base frame isinstalled between lower regions of the towers, thus tying the towerstogether to form a suitably rigid and stable rig base structure. Thetowers may be provided with height adjustment mechanisms (e.g.,hydraulic jacks) to facilitate leveling the base structure over unevenground surfaces. As well, the towers may optionally be provided with“walking” mechanisms whereby the lateral positions of the towers can beadjusted prior to installation of the horizontal base frame. The walkingmechanisms can be coupled for cooperative actuation to facilitatelateral movement of the completed rig base structure.

A drill floor can then be constructed over the horizontal base frame ofthe rig base structure. The drill floor may comprise multiple slabsections that are anchored to each other after being positioned over thebase frame to form an integral drill floor structure. Optionally, thehorizontal base frame can be advantageously set at a height above groundcorresponding to the level of a flatbed truck or trailer, thusfacilitating unloading of drill floor sections by shifting themlaterally off the trailer bed onto the base frame. The drill floor ismated to the towers with suitable guide means such that the drill floorcan be uniformly elevated relative to the towers, with the towers actingto provide lateral stability to the drill floor at all stages of thefloor-elevating process. When the drill floor has been elevated to therequired elevation, it is locked to the towers by any suitable means,such as but not limited to hydraulic clamps.

In a preferred embodiment, the drill floor is elevated using only therig's traveling block and drawworks. To enable this mode of operation,sheave assemblies are mounted to and under the drill floor adjacent toeach tower. Each tower has a floor-lifting cable anchored to an upperregion of the tower and disposable under and around the correspondingsheave assembly associated with the drill floor, such that the free(i.e., non-anchored) ends of the floor-lifting cables converge toward acentral area of the drill floor. After the rig mast has been erectedusing the traveling block and drawworks, the free ends of allfloor-lifting cables can be engaged by the traveling block hook. Thedrawworks can then be actuated to raise the drill floor in onecontinuous operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments in accordance with the present disclosure will now bedescribed with reference to the accompanying figures, in which numericalreferences denote like parts, and in which:

FIG. 1 is an elevation illustrating the unloading of base towers from atransport truck and positioning of the towers on a wellsite.

FIG. 2 is an elevation illustrating a horizontal base frameinterconnecting the rig towers.

FIG. 3A is a first elevation view of an embodiment of a drilling rigstructure in accordance with the present disclosure, showing the drillfloor installed over the horizontal base frame, with a rig mast in anearly stage of erection upon the drill floor.

FIG. 3B is a second elevation view of the assembly in FIG. 3A.

FIG. 4A is a first elevation view similar to FIG. 3A, after completeerection of the rig mast, with the floor-raising cables engaging thetraveling block hook in preparation for elevating the drill floor.

FIG. 4B is a second elevation view of the assembly in FIG. 4A.

FIG. 5A is a first elevation view similar to FIG. 4A, after the drillfloor has been elevated and the rig is ready to be put into service.

FIG. 5B is a second elevation view of the assembly in FIG. 5A.

FIG. 6 is a plan cross-section through the base towers of one embodimentof a drilling rig structure and drill floor layout in accordance withthe present disclosure, prior to elevation of the drill floor.

DETAILED DESCRIPTION

FIGS. 1 through 5B progressively illustrate the steps involved inassembling one embodiment of a transportable drilling rig in accordancewith present disclosure. FIGS. 1 and 2 depict the delivery andpositioning of a plurality of base towers 10 at a drill site. Preferably(but not necessarily), towers 10 will be provided with adjustment means12 for adjusting their height, lateral position, and vertical alignment.Persons skilled in the art will know that such means can be provided ina variety of ways using known technologies, and such means do notconstitute components of the broadest embodiments of drilling rigs inaccordance with this disclosure.

After the required number of towers 10 are in their required positionsrelative to the centerline CL_(W) of a wellbore to be drilled using therig being constructed, a base frame 20 is constructed or installed asshown in FIG. 2, interconnecting the base towers 10. Base frame 20 canbe of any suitable layout and structural configuration. The structurecan also be assembled off the well and “walked” into drilling positionif equipped with adjustment means 12.

As seen in FIG. 3, a drill floor 30 is then constructed over andtemporarily supported on base frame 20, whereupon a rig mast structure100 can be erected upon drill floor 30. The structural details of therig mast and the methods by which it is erected are not directlyrelevant to the subject matter sought to be protected hereby. Forillustration purposes, however, rig mast 100 is shown as a bootstrapmast of the type described previously herein, comprising:

-   -   a bottom mast section 110 with support legs 112 and 114 anchored        at their lower ends 112L and 114L to corresponding anchorages        112X and 114X on drill floor 30;    -   a top mast section 120 fitted with a crown block 122 and        traveling block 124 (as previously described);    -   one or more intermediate mast sections 130 adapted for        connection to top mast section 120 and adjacent mast sections        130 (as previously described).

As seen in FIG. 3A and in greater detail in plan view in FIG. 6, drillfloor 30 is provided with a suitable drawworks (generally indicated byreference number 40), including a cable drum 42 which carries wire ropeused for a drill line fed up and through crown block 122 and down totraveling block 124 as previously described. In the embodimentillustrated in FIG. 6, the rig structure includes four base towers 10laid out in a rectilinear pattern. Drill floor 30 is configured in thegeneral shape of a cross, with adjacent “arms” of the cross fittedclosely around their associated base tower 10. Reference numbers 35denote drill floor guide and anchorage means to facilitate stable anduniform vertical movement of drill floor 30 relative to base towers 10during drill floor lifting operations, and for anchoring drill floor 30to base towers 10 after drill floor 30 has been elevated to its intendedposition for drilling operations. Although indicated for convenience bya single reference number 35, the drill floor guide means and the drillfloor anchorage means may be separate and independent mechanisms.

The location and general configuration of the drawworks (including cabledrum 42) are indicated by reference number 40; in the illustratedembodiment, drawworks 40 is at least partially installed on acantilevered section of drill floor 30. In the illustrated embodiment,drill floor 30 incorporates a rotary table 135 for rotating a drillstring. A driller's control cabin is indicated by reference number 44.Drill floor 30 may have one or more cantilevered catwalks 31 for workeraccess.

Mounted to (and typically underneath) drill floor 30 are a plurality ofsheave assemblies for use in elevating drill floor 30. For clarity inthis patent document, the sheaves used for this particular purpose willbe referred to as drill floor sheaves. One exemplary drill floor sheavearrangement is illustrated in FIGS. 3A through 5B, and in greater detailin FIG. 6. In this exemplary arrangement, an outer drill floor sheave32A and an inner drill floor sheave 32B are provided in association witheach base tower 10, with the rotational axes of inner and outer drillfloor sheaves 32A and 32B being parallel and transverse to a radial lineextending from their associated base tower 10 to well centerline CL_(W).Although drill floor sheaves 32A and 32B in the illustrated embodimentare actually mounted below or within the structure of drill floor 30,they are shown in solid outline in FIG. 6 for purposes of clarity.

In the illustrated embodiment, there is a set of drill floor sheaves foreach base tower 10, but this is not essential. Alternative embodimentscould have one or more base towers 10 that do not have an associateddrill floor sheave assemblies. Furthermore, although in the illustratedembodiment each drill floor sheave assembly includes a pair of drillfloor sheaves, alternative embodiments could use drill floor sheaveassemblies comprising more than two drill floor sheaves or possibly onlyone drill floor sheave.

In FIGS. 3A and 3B, upper mast section 120 has been positioned andpinned to bottom mast section 110, and a first intermediate mast section130 has been positioned within bottom mast section 110 and connected toupper mast section 120. As seen with particular clarity in FIG. 3B,mast-raising cables 135 anchored to upper regions of bottom mast section110 extend around sheaves 132 at the lower end of the intermediate mastsection 130 disposed within bottom mast section 110 and upward forengagement with traveling block 124. Drawworks 40 is then actuated toraise traveling block 124 and lift the assembly of upper mast section120 and intermediate mast section 130 until the lower end ofintermediate mast section 130 has been raised sufficiently to allowanother intermediate mast section 130 to be positioned within bottommast section 110, and so on until rig mast 100 has been constructed toits final intended height as shown in FIGS. 4A and 4B.

At this stage, the mast-raising cables 135 are disengaged from travelingblock 124. A plurality of floor-raising cables 33, corresponding innumber to the number of drill floor sheave assemblies, are threaded fromanchor points 33X in upper regions of their associated base towers 10,around drill floor sheaves 32A and 32B and then upward for engagement bytraveling block 124, all as seen in FIGS. 4A and 4B. Drawworks 40 isthen actuated to raise traveling block 124, thereby elevating drillfloor 30 to an intended service elevation as seen in FIGS. 5A and 5B.Drill floor 30 is then anchored to base towers 10 by suitable anchoragemeans 35 (which by way of non-limiting example could be provided in theform of hydraulic latches).

Although the drawworks and traveling block are used to elevate drillfloor 30 for purposes of embodiments illustrated herein and previouslydescribed, alternative embodiments of rig systems in accordance with thepresent disclosure could use different means for elevating drill floor30. By way of non-limiting example, a worm gear drive unit could be usedto elevate drill floor 30, with guide rollers, and mating racks builtinto base towers 10 at each corner of drill floor 30. The worm geardrive mechanism could be actuated by any suitable power means, such ashydraulic or electric motors. In one alternative embodiment, a worm geardrive could be provided as a supplement or back-up to a primarycable-implemented floor-raising mechanism.

It will be readily appreciated by those skilled in the art that variousmodifications to embodiments in accordance with the present disclosuremay be devised without departing from the scope and teaching of thepresent teachings, including modifications which may use equivalentstructures or materials hereafter conceived or developed. It is to beespecially understood that the scope of the present disclosure is notintended to be limited to described or illustrated embodiments, and thatthe substitution of a variant of a claimed element or feature, withoutany substantial resultant change in functionality, will not constitute adeparture from the scope of the disclosure.

In this patent document, any form of the word “comprise” is to beunderstood in its non-limiting sense to mean that any item followingsuch word is included, but items not specifically mentioned are notexcluded. A reference to an element by the indefinite article “a” doesnot exclude the possibility that more than one of the element ispresent, unless the context clearly requires that there be one and onlyone such element.

Relational terms such as “parallel” and “horizontal” are not intended todenote or require absolute mathematical or geometric precision.Accordingly, such terms are to be understood in a general rather thanprecise sense (e.g., “generally parallel” or “substantially parallel”)unless the context clearly requires otherwise.

Wherever used in this document, the terms “typical” and “typically” areto be interpreted in the sense of representative or common usage orpractice, and are not to be understood as implying invariability oressentiality.

1. A drilling rig system comprising: (a) a plurality of base towersspaced apart in a selected layout; (b) a horizontal base frameinterconnecting lower regions of the base towers to form a basestructure; (c) a drill floor overlying the base frame and verticallymovable relative thereto; and (d) floor-lifting means, for elevating thedrill floor above the base frame.
 2. A drilling rig system as in claim 1wherein: (a) the drill floor incorporates a plurality of floor-liftingsheave assemblies, each said floor-lifting sheave assembly beingassociated with one of the base towers; (b) a plurality of floor-liftingcables, each said floor-lifting cable being anchored to an upper regionof one of the base towers; and (c) the floor-lifting means comprises adrawworks and traveling block associated with a rig mast erected on thedrill floor; such that the floor-lifting cables can be threaded aroundthe associated floor-lifting sheave assemblies and extended upward toengage the traveling block, whereupon actuation of the drawworks willcause the traveling block to move upward within the rig mast, therebyelevating the drill floor relative to the base structure.
 3. A drillingrig system as in claim 1, further comprising locking means for lockingthe drill floor to the base towers to maintain the drill floor at adesired elevation.
 4. A drilling rig system as in claim 3 wherein thelocking means comprises hydraulic latches.
 5. A drilling rig system asin claim 1, further comprising guide means associated with the basetowers, to promote uniform upward movement of the drill floor and toprovide lateral stability to the drill floor during drill floor raisingoperations.
 6. A drilling rig system as in claim 1, further comprisingadjustment means for adjusting the vertical and lateral positions of thebase towers.
 7. A drilling rig system as in claim 1 wherein thefloor-lifting means comprises a plurality of worm gear drive mechanismsand a plurality of mating rack gears, with each rack gear beingincorporated into one of the base towers and one worm gear drive beingincorporated into the drill floor adjacent to an associated rack gear.8. A drilling rig system comprising: (a) a plurality of base towersspaced apart in a selected layout; (b) a horizontal base frameinterconnecting lower regions of the base towers to form a basestructure; and (c) a drill floor overlying the base frame and verticallymovable relative thereto; and (d) floor-lifting means, for elevating thedrill floor above the base frame; wherein: (e) the drill floorincorporates a plurality of floor-lifting sheave assemblies, eachfloor-lifting sheave assembly being associated with one of the basetowers; (f) a plurality of floor-lifting cables, each floor-liftingcable being anchored to an upper region of one of the base towers; and(g) the floor-lifting means comprises a drawworks and traveling blockassociated with a rig mast erected on the drill floor; such that thefloor-lifting cables can be threaded around the associated floor-liftingsheave assemblies and extended upward to engage the traveling block,whereupon actuation of the drawworks will cause the traveling block tomove upward within the rig mast, thereby elevating the drill floorrelative to the base structure.
 9. A drilling rig system as in claim 8,further comprising locking means for locking the drill floor to the basetowers to maintain the drill floor at a desired elevation.
 10. Adrilling rig system as in claim 9 wherein the locking means compriseshydraulic latches.
 11. A drilling rig system as in claim 8, furthercomprising guide means associated with the base towers, to promoteuniform upward movement of the drill floor and to provide lateralstability to the drill floor during drill floor raising operations. 12.A drilling rig system as in claim 81, further comprising adjustmentmeans for adjusting the vertical and lateral positions of the basetowers.
 13. A method for assembling a drilling rig structure, comprisingthe steps of: (a) positioning a plurality of base towers in spacedrelationship in a selected layout at a wellsite; (b) erecting ahorizontal base frame interconnecting lower regions of the base towersto form a base structure; (c) erecting a drill floor overlying the baseframe and vertically movable relative thereto, said drill floorincorporating a plurality of floor-lifting sheave assemblies, each saidfloor-lifting sheave assembly being associated with one of the basetowers; (d) erecting a rig mast on the drill floor, including adrawworks and a traveling block; (e) anchoring a floor-raising cable atan upper region of each base tower; (f) threading the floor-raisingcables around their associated floor-lifting sheave assemblies andengaging the free ends of the cables with the traveling block; (g)actuating the drawworks so as to raise the traveling block and the drillfloor relative to the base structure, until the drill floor is at adesired elevation; and (h) engaging locking means to lock the drillfloor to the base towers.
 14. A method as in claim 13 wherein thelocking means comprises hydraulic latches.
 15. A method as in claim 13,further comprising the step of providing guide means in association withthe base towers, to promote uniform upward movement of the drill floorand to provide lateral stability to the drill floor during drill floorraising operations.
 16. A method as in claim 13 wherein the base towersare provided with adjustment means for adjusting the vertical andlateral positions of the base towers.